Rapid Shift

1 ppb higher daily ozone causes extra deaths

Exposure over short periods of time to particulate matter and ozone air pollution levels below current national safety standards is still associated with premature death amongst US seniors, a new study from the Harvard TH Chan School of Public Health has found. Amongst elderly people who were female, self-identified as black, or low-income, this association was even higher than with the general trend.

“This the most comprehensive study of short-term exposure to pollution and mortality to date,” commented study author Francesca Dominici, a professor of biostatistics and co-director of the Harvard Data Science Initiative. “We found that the mortality rate increases almost linearly as air pollution increases. Any level of air pollution, no matter how low, is harmful to human health.”

Which is more or less what “common sense” would tell you, so this is all probably fairly unsurprising to many people — but also something that flies in the face of many of the “official” positions of recent decades.

The press release provides more: “The researchers assessed daily air pollution exposures using prediction models that provided accurate estimates of PM2.5 and ozone for most of the US, including unmonitored areas. They then linked the air pollution data with mortality data from the entire US Medicare population residing in 39,182 zip codes (93% of all the zip codes in the US), over a 13-year period from 2000-2012.

“During the study period, 22 million people in the study population died. The study found that, for each 10 μg/m3 daily increase in PM2.5 and 10 ppb daily increase in warm-season ozone, the daily mortality rate increased by 1.05% and 0.51%, respectively. While this may seem a small increase, the public health impact is enormous if it’s applied to the whole US population of seniors, according to the study authors.

For example, an increase of just 1 μg/m3 in daily PM2.5 over the course of one summer in the US would lead to 550 extra deaths per year and 7,150 extra deaths over the course of the 13-year study period.

An increase of just 1 ppb in daily ozone over the summer would lead to 250 extra deaths per year or 3,250 extra deaths over 13 years.”

Pretty substantial increases, all things considered.

As noted earlier in the article, various sub-groups of the population experienced much greater susceptibility than others — with the Medicaid-eligible (used as a proxy for low-income people) seeing a mortality increase link (with PM2.5) 3 times higher than that of other groups. “Nonwhites” and women see a mortality risk around 25% higher than whites and men, respectively.

The researchers speculated that poverty and unhealthy lifestyles may play a part in the disparity.

This work follows on an earlier study from the same group that found that long-term exposure to air pollution levels below the national standards for long-term exposure still resulted in an increased risk of early death.

“No matter where you live — in cities, in the suburbs, or in rural areas — as long as you breathe air pollution, you are at risk,” explained Qian Di, the lead author of the new study, and a PhD student in the Department of Environmental Health.

The new study is detailed in a paper that was published on December 26th in the Journal of the American Medical Association (JAMA).